Add consts and gas_mixtures with initial calculations

src/mixtures/gas_mixture.rs

@@ -0,0 +1,79 @@
+use crate::{
+    consts::P_REF,
+    properties::{
+        thermo_fit::{Phase, SpeciesThermoData},
+        transport_fit::SpeciesTransportData,
+    },
+};
+
+pub struct GasMixture {
+    pub(crate) ns: Vec<f64>,
+    pub(crate) nsum: f64
+    pub(crate) species: Vec<SpeciesThermoData>,
+    pub(crate) transport_data: Vec<SpeciesTransportData>,
+}
+
+impl GasMixture {
+    // Calculate the normalized chemical potential (μ/RT) for each component in the mixture.
+    //
+    // Equations 2.11 from reference paper
+    pub fn gas_chem_potentials_over_rt(&self, temp: f64, pressure: f64) -> Vec<f64> {
+        self.ns
+            .iter()
+            .zip(self.species.iter())
+            .map(|(n, s)| -> f64 {
+                match s.phase {
+                    Phase::Gas => {
+                        let p = s
+                            .polynomial_at(temp)
+                            .expect("Gas doesn't have a polynomial");
+                        p.h_over_rt(temp) - p.s_over_r(temp) + (pressure / P_REF).ln() + (n/self.nsum).ln()
+                    }
+                    Phase::Condensed => todo!(),
+                }
+            })
+            .collect()
+    }
+    
+    // Calculate the normalized entropy (S/R) for each mixture component
+    //
+    // Equations 2.17 from reference paper
+    pub fn gas_entropies_over_rt(&self, temp: f64, pressure: f64) -> Vec<f64> {
+        self.ns
+            .iter()
+            .zip(self.species.iter())
+            .map(|(n, s)| -> f64 {
+                match s.phase {
+                    Phase::Gas => {
+                        let p = s
+                            .polynomial_at(temp)
+                            .expect("Gas doesn't have a polynomial");
+                        p.s_over_r(temp) - (n/self.nsum).ln() - (pressure/P_REF).ln()
+                    }
+                    Phase::Condensed => todo!(),
+                }
+            })
+            .collect()
+    }
+    
+    // Calculate the normalized mixture enthalpy (H/RT)
+    // Note that the enthalpy doesn't have a dependence on the pressure.
+    // Equation 2.14 from the paper
+    pub fn mixture_h_over_rt(&self, temp: f64) -> Vec<f64>{
+         self.ns
+            .iter()
+            .zip(self.species.iter())
+            .map(|(n, s)| -> f64 {
+                match s.phase {
+                    Phase::Gas => {
+                        let p = s
+                            .polynomial_at(temp)
+                            .expect("Gas doesn't have a polynomial");
+                        n*p.h_over_rt(temp)
+                    }
+                    Phase::Condensed => todo!(),
+                }
+            })
+            .collect()       
+    }
+}